Add a map prompt to ohmage

[shankari]

ohmage is a platform for displaying dynamically created surveys to users based on location, time of day, etc, and collating and displaying the results. They support a bunch of different prompts - choice, text, etc, but not map. I would like to have a map prompt or at least, a map display.

The ohmage team has added a map prompt for android. We would like to add one for iOS.

[shankari]

The easiest thing to do is to probably look at the changes for android and port them to iOS.

On android, the map_prompt is implemented in this branch (https://github.com/smalldatalab/android-ohmage/tree/map_prompt). You can see the major changes in this commit (smalldatalab/android-ohmage@85a0998).
In particular, there are a new MapPrompt.java and map_prompt.xml that respectively define the logic and ui of the map prompt.

A survey that has the map prompt is over here: http://pastebin.com/RGjdw3pe

What map prompt does is to render the corresponding prompts (i.e. the first two in the survey) and collect the user's selection on the map.

[shankari]

After I looked at the android and iOS code, I had the following questions for the original developer.

1. I know this is not related to the main change, but in your commit, you stop registering the type adapter for the double. Is this intentional? Do I need to do it on iOS as well?
2. I briefly poked around the code, and I think that, at a high level, I would need to add a new model that represents the lat-lng of the map to the set of models at:
   https://github.com/smalldatalab/ios-ohmage/tree/master/ohmage_ios/Model
3. In that case, what is the difference between the Model directory above and the _Model subdirectory here: https://github.com/smalldatalab/ios-ohmage/tree/master/ohmage_ios/Model/_Model
4. I think that I will then have to add a new item type to:
   https://github.com/smalldatalab/ios-ohmage/blob/master/ohmage_ios/OHMSurveyItemTypes.m
   and set it up properly by adding a new method similar to this one:
   https://github.com/smalldatalab/ios-ohmage/blob/master/ohmage_ios/OHMSurveyItemViewController.m#L491
   Is that correct?
5. However, there is already a MapViewController defined here:
   https://github.com/smalldatalab/ios-ohmage/blob/master/ohmage_ios/OHMLocationMapViewController.m
   can he provide some idea of what it is used for? It looks like it is used to edit locations for reminders. Is that functionality only on iOS? I don't see it in the android client....

[shankari]

First response:

1. It is not related to the main change. I removed it because it causes infinite loop ( it is a double serializer but itsell generate another double to be serialized.)

[shankari]

Second response:

As mentioned in the repo docs, I used Mogenerator to build the CoreData model in ohmage. To add a new location prompt type, here are the steps you will need to perform:

iOS:

1. Download and install Mogenerator
2. Add a new model version (select ohmage_ios.xcdatamodel in the Model folder then from the “Editor” menu select “Add model version”, then from the properties pane set the current version to the newly-created version)
3. Add latitude/longitude attributes to the OHMSurveyPromptResponse entity
4. Select the “Mogenerator” target from the build targets menu and build the target. That will add properties for the new attributes to the OHMSurveyPromptResponse class.
5. Add a new prompt type to the enum in OHMSurveyItemTypes.h and a string name for the prompt type to the itemTypeDictionary in OHMSurveyItemTypes.m
6. Create a view controller to handle location prompts. It would be possible to simply add all the logic and map UI to the OHMSurveyItemViewController class, but probably easier to subclass that class since maps are so much more involved than all the existing prompt types. If going the subclass route, add a check for prompt type in pushNextItemViewController (line 640) or in the init method (line 65) and return an instance of the subclass for location prompts.
7. Add logic to create a json representation of the location prompt response in OHMSurveyPromptResponse.m (line 231)

Backend:

1. Add the new prompt type to the prompt type definitions on the backend so survey definitions that include that prompt type don’t fail validation (Andy, you’ll have to explain how you did that for the VAS prompt)
2. Add logic for parsing the json representation of location prompts (from step 7 above) on the backend (again, Andy, I defer to you)

Come to think of it, it might be easier to store the lat/long pairs in a string. That would allow you to skip steps 1-4 from the iOS section and step 2 from the Backend section. Just store the serialized location string in the “stringValue” property of the existing version of OHMSurveyPromptResponse, and return that value for step 7 above.

You can probably reuse some code from the OHMLocationMapViewController class, but it is pretty customized for setting up location-based reminders so it won’t be very helpful as-is.

[shankari]

I believe that the backend changes are already done, since Andy has implemented the prompt for android. Once you are done reading, understanding and maybe experimenting with the iOS side, I can reach out to Andy again and confirm.

I just don't want to get his hopes up too high since that might be a while... :)